Definition - What does Corona mean?
The corona is a flower component in certain types of plants, from the Passion Flower and Lilly families for example. The corona is a set of adaxial appendages growing from the corolla, or the outer edge of stamens. Also known as the paraperigonium, paraperigon and paracorolla. The corona is located on the perianth of a flower. This is one of the non-reproductive parts of the flower. The perianth is composed of the petal, sepal, calyx and corolla.
MaximumYield explains Corona
In layman's terms, this means that the perianth is composed of the petals and the green semi-leaves underneath the petals that would envelope the developing bud before it becomes a flower. The corona is considered to be a modified calyx, and is also called corona because of being shaped like a crown. Corona is Spanish for "crown." The crown-shaped outgrowth at the center of a daffodil or narcissus flower is also known as the corona.